The present invention relates to a brake pad for a bicycle.
In the field of racing bicycles the use is now widespread of components made of composite materials, such as for example materials made up of carbon fibres embedded in a matrix of polymeric material. Amongst the components made with these materials, rims for bicycle wheels are highly appreciated because of the excellent combination of strength, elasticity and lightness that it is possible to achieve.
However, it has been found by the inventors of the present invention that the rims made in this way require brake pads having high performance, both in dry and in wet conditions.
The inventors of the present invention have also found that rims made of composite materials, in particular of carbon fibre, can have problems after intense braking action due to two main factors. The brake pads, in fact, rubbing on the rim, can cause an abrasion of the rim and generate heat up to 200° C. that alters the mechanical characteristics of the polymeric matrix in which the carbon fibres are embedded. Delamination of the rim can thus occur. In extreme cases the rim can break or braking may not occur with serious consequences for the safety of the cyclist.
Finally, it has been found by the inventors of the present invention that known pads obtained by cross-linking a mixture comprising: rubber consisting of a polymer selected from acrylonitrile-butadiene (NBR), hydrogenated acrylonitrile-butadiene (HNBR), styrene-butadiene (SBR), ethylene-propylene (EPR, EPDM), chloroprene (CR), or combinations thereof, cork and expanded natural graphite having a high heat conductivity, as described for example in European patent EP 2030806 in the name of the same Applicant, have a braking performance and a wear resistance that are not entirely satisfactory, in particular when used with the aforementioned rims made of composite material.
The problem underlying the present invention is that of overcoming the aforementioned problems, improving the braking performance of the pad both in dry and in wet conditions, ensuring at the same time a lower wear of the pad.
Consequently, the present invention relates, in a first aspect thereof, to a brake pad, in a second aspect thereof, to a wheel-brake assembly, and in a third aspect thereof, to a mixture for the preparation of a brake pad.